amd64 slower than i386 on identical AMD 64 system? / How is hyperthreading handled on amd64?

[Alexander Konovalenko]

> Hi
> Since some time (>6.0R) I have the impression that amd64 runs slower than 
> i386. Now I run some tests on identical hardware and using ubench confirmes 
> this. Somebody has comments on this?

I have Dual core AMD64 4400+ and FreeBSD RELENG_5. I don't have FreeBSD i386 
installed but you can just compare benchmarks.

ubench uses all CPU/cores by default, when one ubench is running, top shows:

 PID USERNAME   PRI NICE   SIZE    RES STATE  C   TIME   WCPU    CPU COMMAND
11528 XXXX       111    0  3572K   880K RUN    1   0:12 93.64% 42.29% ubench
11529 XXXX       111    0  3572K   880K CPU0   1   0:11 97.21% 41.16% ubench
11526 XXXX        -8    0  3572K   880K piperd 0   0:17 41.76% 31.98% ubench


one ubench executed (with no -s flag = use all CPU, default):

Unix Benchmark Utility v.0.3
Copyright (C) July, 1999 PhysTech, Inc.
Author: Sergei Viznyuk <sv at phystech.com>
http://www.phystech.com/download/ubench.html
FreeBSD 5.5-PRERELEASE FreeBSD 5.5-PRERELEASE #12: Sun Mar  5 17:34:07 CET 
2006     XXXX at XXXX:/usr/obj/usr/src/sys/DAEMON64SMP amd64
Ubench CPU:   238149
Ubench MEM:   255459
--------------------
Ubench AVG:   246804


two ubench executed with -s flag (use single CPU only):

Ubench Single CPU:   120184 (0.40s)
Ubench Single MEM:   126787 (0.39s)
-----------------------------------
Ubench Single AVG:   123485

Ubench Single CPU:   121000 (0.41s)
Ubench Single MEM:   128762 (0.40s)
-----------------------------------
Ubench Single AVG:   124881


one ubench executed with -s flag (use single CPU only):

Ubench Single CPU:   123251 (0.40s)
Ubench Single MEM:   161494 (0.40s)
-----------------------------------
Ubench Single AVG:   142372


/Alexander Konovalenko

+46-8-5537-8142 (office)
+46-7-3752-2116
http://daemon.nanophys.kth.se/~kono

Royal Institute of Technology (KTH)
Nanostructure Physics Department, Albanova
Roslagstullsbacken 21
10691 Stockholm
Sweden